I use ’tmux’ on anything that runs it, from FreeBSD, macOS and Linux.

One some of Linux servers, noticably openSUSE ones, when I connect to them via SSH, I would receive the following warning:

Have a lot of fun...
warning: Could not set up terminal.
warning: TERM environment variable set to 'tmux-256color'.
warning: Check that this terminal type is supported on this system.
warning: Using fallback terminal type 'ansi'.

What worse is that, when I switch to root account, the backspace key doesn’t work correctly. For example, hitting backspace will produce a space instead.

How can I fix this? By setting the variable TERM='xterm'.

➜ export TERM='xterm'
➜ ssh tc2
Have a lot of fun...
Welcome to fish, the friendly interactive shell
Type help for instructions on how to use fish

Some also suggested to set th set the default value in the ~/.tmux.conf as the follwoing:

set -g default-terminal "xterm"

And how did I find this out? Of course, by searching for similar problem on the internet. Full credit goes to the owner of the article below.